Authors: Nan Zou, Shu-Ta Yeh, Gang-Len Chang, Alvin Marquess, and Michael Zezeski
Journal: Transportation Research Record, No. 1922, 2005, pp. 138–148.
Abstract:
This paper presents a simulation-based system for Ocean City, Maryland, evacuation during hurricanes. The proposed model features integration of optimization and simulation that allows potential users to revise the optimized plan for both planning and real-time operations. Since it is difficult to capture all network operational constraints and driver responses fully with mathematical formulations, six evacuation plans for Ocean City were investigated. Each was optimized initially with the optimization module and then revised on the basis of the results of simulation evaluation. To address potential incidents during the evacuation, the study presents a real-time operation plan with a developed system that allows the responsible operators to concurrently evaluate all candidate responsive strategies and to track the performance over time of the implemented strategy.
Authors: Ying Liu, Xiaorong Lai, and Gang-Len Chang
Journal: Transportation Research Record, No. 1964, 2006, pp 127-135
Abstract:
Staged evacuation is widely used under emergency situations where different parts of the target network may suffer different levels of severity over different time windows. By evacuating those populations in the network via an optimized sequence, the staged evacuation strategy can best utilize the available roadway capacity, optimally distribute the total demand over the evacuation time horizon, and thus minimize the network congestion level. This study has proposed a cell-based network model to capture critical characteristics associated with the staged evacuation operations. The proposed model features its capability in reflecting incident impacts and arrival patterns of evacuees in computing the optimal starting time and routes for each evacuation zone. The preliminary numerical results have demonstrated the potential for applying the proposed staged evacuation model in real-world emergency management and planning.
Click the image to visit traffic monitoring system for Maryland highways.
Authors: Yue Liu, Gang-Len Chang, Ruihua Tao, Thomas Hicks, and Eric Tabacek
Journal: Transportation Research Record, In press (presented in Transportation Research Board 86th Annual Meeting, January, 2007)
Abstract:
In this paper the author presents the results of our empirical study on the distribution of dilemma zones for different groups of drivers at signalized intersections. Using a specially designed video-based system, this study has conducted extensive field observations of 1123 drivers’ responses to a yellow phase at six intersections of high accident frequency, including all critical data such as the speed evolution during the yellow phase, the acceleration/deceleration rates, and the approximate reaction time to an encountered yellow phase. Our empirical results have revealed that the dilemma zone is dynamic in nature with its location varying with the driving populations, and the commonly used practice of extending the yellow phase duration recommended may not eliminate all the dilemma zones.Two types of strategies which can effectively eliminate the dynamic dilemma zones are also designed to improve intersection safety.
Download paper by clicking here
Authors: Ning Yang, Gang-Len Chang, and Kyeong-Pyo Kang
Journal: Journal of Transportation Engineering, 2007
Abstract:
This paper presents a new lane-based signal merge (LBSM) control system for freeway work zone operations. The proposed system applies the signal control concept to regulate the vehicles passing the work zone area at a lane-by-lane basis and offers an effective way to maximize the operational efficiency as well as safety. Introduction of the preliminary configuration and principal components associated with the proposed LBSM control contribute the core of this study.
To evaluate the effectiveness of the proposed system, this study has also conducted extensive simulation experiments, based on a freeway simulator calibrated with real-world work zone data. The experimental results show that under heavily congested traffic conditions the LBSM can outperform all existing control strategies with respect to the work zone throughput, the average vehicle delay, the average stop delay, and the average number of stops. This study has also investigated critical traffic flow related factors that may impact on the performance of such a system.
Authors: Yue Liu, Gang-Len Chang, Ying Liu and Xiaorong Lai
Conference: 2008 TRB Annual Meeting
Status: Accepted for Presentation
Abstract:
Evacuating large municipal areas during emergencies and disasters in an efficient manner is one of the critical tasks of emergency management agencies. This paper presents a corridor-based emergency evacuation system and its example applications for the Washington D.C. metropolitan area. The proposed system features its flexibility in accounting for various critical issues associated with both planning and real-time operations, including multiple data source integration, network decomposition, network-level traffic routing, contra-flow design, staged evacuation, optimal signal timing, and incorporating pedestrian and bus operations. Under a hypothetical emergency scenario for Union Station, the proposed system has demonstrated its effectiveness for producing evacuation routing strategies, identifying potential bottlenecks, and evaluating the performance of evacuation operations.
Authors: Yue Liu, Gang-Len Chang, and Jie Yu
Journal: ASCE Journal of Transportation Engineering
Abstract:
This paper presents the analysis results of driver responses during a yellow phase, based on field observations of 1123 drivers collected with a specially-designed system from six signalized intersections of high crash frequency in Maryland. By classifying drivers into aggressive, conservative, and normal groups based on their responses (i.e., stop or pass) and the distances to the stop line when the signal turns yellow, the statistical tests with the ordered-probit model clearly indicate some critical factors and their impacts on a driver’s decision at intersections. Such factors include average traffic flow speeds, traffic volume rate, the green split, the number of through and crossing lanes in the target approach, signal coordination, the difference between a vehicle’s approaching speed and the average traffic flow speeds, a driver’s gender, age, talking over cell phone or not, a vehicle’s type and model, and etc. The research findings for this study offer the basis for responsible agencies to identify underlying factors contributing to aggressive maneuvers at signalized intersections which often cause traffic crashes, and to develop improvement strategies, such as customized driver education and intelligent safety protection systems.
Authors: Jie Yu, Yue, Liu, and Gang-Len Chang
Journal: Journal of Transportation Engineering ASCE
Abstract:
This paper presents a comprehensive model for ranking candidate location plans of multiple urban transit hubs, which can effectively capture various aspects of concerns in the transit hub location planning process, including the overall efficiency of the transit network, the transfer intensity, the proximity to major passenger generators/attractors, the effectiveness of hub service coverage, the compatibility with land use restrictions, and the adaptability to future developable transit concepts. Grounded on an Analytical Hierarchy Process (AHP)-based framework integrated with the fuzzy logic, the proposed model offers the strengths to effectively determine the weights for multiple evaluation criteria, and to synthesize the final score of each candidate plan for comparison. Results from a case study in Suzhou Industrial Park, China reveal that the proposed model offers some promising properties for transportation planners to use in planning of transit hub locations. Comparative studies with respect to different evaluation criteria has further demonstrated the effectiveness of the proposed model in capturing the impacts of different criteria on the decision making process.
Authors: Yue, Liu and Gang-Len Chang
Journal: Transportation Research Part C， 2010
Abstract:
This paper presents an arterial signal optimization model that features its effectiveness on: (1) explicitly modeling physical queue evolution on arterial links by lane-group to account for shared-lane traffic interactions; and (2) capturing the dynamic interactions of spillback queues among lane groups and between neighboring intersections due to high demand, geometric constraints, or signal settings. Depending on the detected traffic patterns, one can select the control objective to be either minimizing the total travel time or maximizing the total throughput over the target area. The solution procedures developed with the Genetic Algorithm (GA) have been tested with an example arterial of four intersections under different demand scenarios. Extensive experimental analyses in comparison with results from TRANSYT-7F (version 8) reveal that the proposed model and solution method are quite promising for use in design of arterial signals, especially under congested, high demand traffic conditions.
Authors:Yongjie Lin, Xianfeng Yang, Gang-Len Chang, and Nan Zou
Journal: Transportation Research Record: Journal of the Transportation Research Board, No. 2356, 2013
Abstract:
This paper presents a transit signal priority (TSP) model designed to consider the benefits both to bus riders and to intersection passenger car users. The proposed strategy, which is mainly for headway-based bus operations, offers the responsible agency a reliable way to determine the optimal green extension or red truncation duration in response to multiple bus priority requests from different routes. The control objective is to minimize bus passenger waiting time at the downstream bus stop while ensuring that the delays for all passengers are not increased. In tests that used field data from Jinan, China, the proposed strategy showed promise in reducing bus passenger waiting time and total intersection delay. Further exploration with simulation experiments for sensitivity analysis found that TSP is most effective if the ratio between bus and passenger volumes exceeds a threshold of 2%.
Download (Transit-Priority-Strategies-for-Multiple-Routes-Under-Headway-Based-Operations.pdf)